Abstract: BACKGROUND: Kirschner wire and tension band internal fixation is the preferred surgical procedure for treating transverse patellar fractures, but it is often associated with postoperative instability, nonunion, and internal fixation failure. Therefore, optimizing the internal fixation method is of great clinical significance.
OBJECTIVE: To investigate the effect of crossed Kirschner wire placement on the fixation of transverse patellar fractures. 
METHODS: A patellar model was constructed using normal lower limb CT scan data. A transverse patellar fracture and Kirschner wire model was further constructed. Parallel, 30°, 45°, and 60° crossed Kirschner wire placement models were designed. Finite element analysis was performed to analyze the fracture surface stress, fracture surface displacement, Kirschner wire stress, and wire stress under five different working conditions (neutral knee position, 5° flexion, 15° flexion, 45° flexion, and 60° flexion).
RESULTS AND CONCLUSION: The fracture surface stresses in the four internal fixation models ranged from 2.06 to 40.00 MPa. The parallel Kirschner wire fixation group had the highest fracture surface stress among all five conditions. The crossed 30° Kirschner wire fixation group had lower fracture surface stress at 15° of knee flexion than the crossed 45° and crossed 60° Kirschner wire fixation groups. The fracture surface displacements in the four internal fixation models ranged from 0.03 to 0.61 mm. The crossed 60° Kirschner wire fixation group had the highest fracture surface displacement at 5° and 15° of knee flexion, the parallel Kirschner wire fixation group had the lowest fracture surface displacement at 5° of knee flexion, and the crossed 30° Kirschner wire fixation group had the lowest fracture surface displacement at 15° of knee flexion. The wire stresses in the four internal fixation models ranged from 56.80 to 2 511.00 MPa. The parallel K-wire fixation group had the highest wire stress at 5° and 15° of knee flexion, and the crossed 30° Kirschner wire fixation group had the lowest wire stress at 5° and 15° of knee flexion. The Kirschner wire stresses in the four internal fixation models ranged from 65.67 to 1 018.00 MPa. The Kirschner wire stress in the 60° crossed Kirschner wire fixation group was highest at 5° of knee flexion, the parallel Kirschner wire fixation group at 15° of knee flexion, and the 30° crossed Kirschner wire fixation group at both 5° and 15° of knee flexion. The results showed that the 30° crossed Kirschner wire placement performed best in terms of fracture stability and stress distribution within the internal fixation system, demonstrating excellent biomechanical advantages. 

Key words: patellar fracture, transverse fracture, Kirschner wire fixation, biomechanics, finite element analysis, orthopedic implant